The invention relates to a method calling a ground station by an aircraft, by the so-called "Calsel" System. A reverse method, viz. for calling an aircraft by a ground station is called the "Selcal" System and is mentioned in "Aeronautical Telecommunications Annex 10 to the Convention on International Civil Aviation," Volume 1, Equipment and Systems, Aug. 22, 1968, p. 119. A drawback of this "Selcal" System or method for aircraft is that too little power is available.